Lubricants and fuels stabilized with antioxidants for high and low temperature conditions



United States Patent 3,320,165 LUBRICANTS AND FUELS STABILIZED WITH ANTIOXIDANTS FOR HIGH AND LOW TEM- PERATURE CONDITIONS Robert F. Bridger, Yardley, Leo J. McCabe, Princeton, and Albert L. Williams, Paulsboro, N.J., assignors to Mobil Oil Corporation, a corporation of New York No Drawing. Filed May 11, 1965, Ser. No. 454,993

g 20 Claims. (Cl. 25249.6)

This invention relates to the stabilization of lubricant and fuel compositions. Particularly this invention relates to additives providing protection against oxidation for such compositions over a broad temperature range.

Oxidation of lubricating oils takes place to a large extent in modern engines operated under normal conditions. The oxidation-deterioration products of oils, being acidic, can seriously corrode the metal surfaces of the engine. Moreover, a lubricant which has been subjected to oxidation cannot disperse the sludge readily, and permits the impurities to settle or become deposited inside the engine. As a result, the engine does not work efliciently.

Commercial lubricants, as well as fuels, are normally blended with agents known as antioxidants to prevent this deterioration. Unfortunately, many known antioxidants are only effective within a given temperature range. For example, if a low temperature antioxidant .is subjected to heat at a high temperature it may be destroyed and the oil medium is susceptible to oxygen attack. On the other hand, although high temperature antioxidants can withstand heat longer, they may be ineffective at lower temperatures, and themselves destroyed. No fluid system in todays automotive or aircraft engines is operated at a constant temperature. A lubricating oil, for example, is continually subjected to high and low temperatures as it circulates through the lubricating system, e.g. from the sump to the engine block. For that reason antioxidant protection must be continuously available at both temperature levels. An oil passing over a high temperature surface must still be able to retain its low temperature antioxidant for protection in the subsequent cooler phase of the lubricating cycle. Conversely, the oil maintained temporarily at lower temperatures must retain its high temperature protection as it passes into the hotter stage. Moreover, this recirculation of oil from cold to hot regions on the system must last over a substantially extended period to be of any economical advantage. In the past, no effective engine lubricating system has been found in which the operating life of the antioxidant is sufficiently extensive.

It is therefore a major object of this invention to provide a novel combination of additives for lubricants and fuels. A further object is to provide an antioxidant composition for lubricants and fuels which is continuously operable at high and low temperatures. Another object'of this invention is to provide antioxidants for lubricants. and fuels which provide mutual protection for each other at high temperatures.

In accordance with this invention, it has now been discovered that lubricating oil and fuel compositions have extended antioxidant protection at varying temperature conditions by adding thereto in combination (1) a 9-hydroxy-or 9-alkoxy-9,l0-boroxarophenanthrene and (2) an alkylated aromatic hydroxy compound having up to 7 aromatic rings or an aromatic secondary amine. Preferably 3,320,165 Patented May 16, 1967 "ice wherein R may be hydrogen, alkyl, a term which includes also substituted alkyl, or alkenyl, cycloalkyl and haloalky-l having from 1 to about 25 carbon atoms. Suitable alkyl substituents for R may be methyl, tert.-butyl, dodecyl, flmethoxyethyl, fi-aminoethyl, oleyl, Z-bicyclohexyl, and 1,1,7-trihydroperfluoroheptyl. The anhydride form of the compound may also be used, in which case R above is Rand R" may be alkyl, halogen or haloalkyl, and may be the same or different for each ring substitution and n is zero or an integer of 1 to 4, and preferably zero or 1 to 2.

The preparation of 9-hyd'roxy-9,l0-boroxarophenanthrene, the preferred additive according to this invention, is achieved by the reaction of ortho-phenylphenol and boron trichloride; the product is heated in the presence of aluminum chloride to give 9-chloro-9,l0-boroxarophenanthrene. The chloro compound is then hydrolyzed to the hydroxy. This procedure is described in detail in the above-mentioned application.

At temperatures of up to about 400' F., this compound is an exceptionally effective antioxidant for lubricating oils. However, it becomes completely degraded in a very short time when exposed to temperatures above tha level.

With respect to the second, or high temperature, component, this may be .an alkylated aromatic hydroxy compound containing from 1 to 7 aromatic rings, such as a polyalkylated polyhydroxy phenol, a polyalkylated naphthol, or a secondary aromatic amine. I

The polyalkylated polyhydroxy phenol has been disclosed as an antioxidant for lubricants in copending US. Ser. No. 355,405, filed Mar. 27, 1964. These compounds include benzene, naphthalene and other aromatics, con taining up to 7 rings either fused or connected by a single bond, as in biphenyl, or by an alkylene atom as in diphenylmethane. The alkyl substituents may have at least 4 carbon atoms attached to the nucleus, with at least 2 alkyl substitutions per compound. The preferred additives in this invention are the polyhydroxy benzenoid compounds having 2 to 3 hydroxy groups and 3 to 4 alkyl substituents with from about 12 to 30 carbon atoms.

An alternative second additive is the polyalkylated naphthol, disclosed in US. patent application Ser. No. 358,375, filed Apr. 8, 1964. These compounds include both alphaand beta-naphthols having at least two alkyl substituents providing a total sum of alkyl carbon atoms of at least 8. Alkyl radicals having about 6 to about 30 carbon atoms are preferred.

A third class of high temperature antioxidants is a secondary aromatic amine having the formula wherein R' may be alkyl having from about 1 to about 25 carbon atoms, cycloalkyl, such as cyclohexyl, heterocyclic in which the cyclic structure has an oxygen, sulfur or second nitrogen atom, and aryl, such as phenyl or naphthyl, and substituted aryl, including such substituents as alkyl with from 1 to about 25 carbon atoms, halo, and haloalkyl, and Ar is an aromatic structure of 1 to 2 benzene rings, with up to five substituents including alkyl with from 1 to about 25 carbon atoms, halo, and haloalkyl; R and Ar may also be part of the same ring as in a heterocyclic structure. The secondary amines of this invention include N-phenyl-l-naphthyl amine, N-phenyl- 2-naphthyl amine, diphenylamine, N,N'-diphenyl-p-phenylene diamine and the dimers thereof, and phenothiazine.

Specific preferred examples of the second component include tri-(2-hexadecyl)hydroquinone, tetra-(C -C -alkyl) resorcinol, tri-(2-hexadecyl)catechol, tris(2-hexadecyl) pyrogallol, tri-dodecyl-l-naphthol, 4,4-methylenebis(2,6-ditertiary-butyl-phenol), and the aforenamed N- phenyl-l-naphthyl amine.

We have discovered in this invention that the second component of these compositions, while performing as a high temperature antioxidant, e.g. at temperatures over 400 F., appears to prevent the heat from destroying the boroxar-ophenanthrene component. Were the first component to be used as the sole antioxidant for a fuel or lubricant composition, it would not function after exposure to high temperatures, e.g. near the engine block. The oil or other preponderant medium would deteriorate under oxidation. If the phenol, or the naphthol or the secondary amine were the sole component, the medium would be poorly protected against oxidation at temperatures below 400 F., in the sump or oil pan, for example, and the additive would be destroyed affording no protection to the oil as it later passes into the engine block. We have theorized that a mutual protection on the part of each additive, one for the other, has been manifested. Not only is the oil or fuel protected but also is the more susceptible additive under the temperature conditions at any instant.

Surprisingly, therefore, the compositions of this invention have longer high and low temperature service life than similar compositions using the components individually, even at higher concentrations. For example, the boroxarophenanthrene antioxidant is known to become deteriorated in several seconds at about 550 F.; in the instant compositions it may remain effective even after many hours of total exposure.

The quantity of the 9-hydroxy or 9-alkoxy-9,10-boroxarophenanthrene or derivative thereof which may be used is in the range of about 0.01% to about 25% by weight of the total composition; and preferably from about 0.01% to about 10% by weight for lubricants and from about 0.001% to about by weight for fuels. The concentration of the high-temperature component is in the range of about 0.1% to about 25% by weight, and preferably about 0.5% to about 5%.

Discussion of the compositions of this invention have centered around lubricating oils and fuels in general; this is meant to include mineral oils, both solvent-refined and acid-refined, hydrocarbon fuel fractions, polyole'fins, dicarboxylic esters, trimethylol esters, pentaerythritol esters, polyalkylene oxides, phosphorus acid esters, silicones and the like. The compositions may therefore find utility not only as lubricants and fuels for automotive engines, but also as gear oils, turbine oils, aviation lubricants, transmission oils, hydraulic fluids, and marine oils. Moreover these formulations may also be combined with suitable thickeners, such as polyaromatic dye compounds or clays, to form oxidation-inhibited greases.

The following examples and tests are intended to illustrate more clearly the inventive concept without being a limitation on any aspect thereof.

PREPARATION OF 9-HYDROXY-9, 10- BOROXAROPHENANTHRENE Into a 1-liter flask were added 200 ml. of dry methylene chloride, held at 70 C. The flask was purged with nitrogen, and 235 grams (2.0 moles) of boron trichloride were bubled in. To the contents were added dropwise, under agitation, 170 grams (1 mole) of ophenylphenol in 200 ml. of methylene chloride, with the nitrogen atmosphere present. The temperature was maintained at 50 to -70 C. After the addition of the phenol, the reaction mass was stirred for 30 minutes at 70 C. and then was allowed to come to room temperature. Hydrogen chloride coming off was trapped in caustic solution. Stirring was continued for an additional hour and excess boron trichloride and methylene chloride were removed at 25 C. and 0.2 mm. Hg.

The brown liquid remaining was dissolved in 200 ml. of hexane and 5 grams of aluminum chloride were added, the mixture being held at 50 C. for 4 hours. Hydrogen chloride evolution ceased at this time. The product was filtered and the filtrate dissolved in 200 ml. of ether. The ether solution was shaken with 400 ml. of water in a separatory funnel. After the mixture was settled and the aqueous phase removed, the organic phase was concentrated under reduced pressure. A solid was formed, which was dissolved and recrystallized in benzene; M.P. 210212 C. The ultra-violet spectrum analysis corresponded to the reported analysis of Deward and Dietz,

.J. Chem. Soc., London, 1960, pages 1344-1347.

Analysis.-Calcd for C H O B: B, 5.5%. Found: B, 5.9%.

The above product was tested in oil as the sole antioxidant and in combination with the aromatic amines and phenols in accordance with this invention.

DESCRIPTION OF TESTS To simulate the conditions of the various parts of an engine lubricating system, the oil compositions are subjected to two tests successively at high and low temperatures. Control tests of fresh compositions are also run to better illustrate the unexpected nature of the invention.

I. Thin-film oxidation test.In this test, the antioxidants are dissolved in a white oil (K.V. 210 F., 8 centistokes). The oil blend sample (140 ml.) is pumped through a preheater where it is heated to 550 to 600 F. and onto a heated aluminum disc contained in an enclosed chamber. The disc, held at 600 F., has a shallow conical face of 12 cm. in diameter and is rotated at 2500 rpm. The rotation causes the oil to spread into a thin film of about 0.0003 inch thickness over the disc surface. The approximate contact time of the oil on the disc is about 1 second. During the disc rotation, a stream of purified air is pumped continuously into the chamber at a constant rate of about 200 liters per hour. As the oil film becomes oxidized, the air that is consumed thereby is replaced automatically from a reservoir and the volume is recorded. The oil leaves the disc at the end of the one-second cycle and is cooled to F. by means of a water jacket. Each sample is subjected to the test for 10 cycles.

II. Low temperature oxidation test.Oxidation tests at a low temperature (302 F.) were conducted in an oxygen circulation apparatus of the type described by Dornte in Ind. Eng. Chem. 28, pages 26 to 30 (1936), modified Then the composition was diluted with 9' further portions of oil; in other words, the new concentration of the combined additives was reduced to of its former level. This dilute composition was tested under the conto record the rate of oxygen absorption automatically. 5 ditions of the low temperature oxidation test at 302 F., Broadly, in this test a tube containing the test oil sample and the induction period was measured. A diluted 'comis placed in a heater equipped with a thermostat control position was prepared as a control sample for each test set at 302 F. After thermal equilibrium is established, sample and tested at 302 F. without the previous exthe sample tube is connected with a closed oxygen circuposure in the thin-film test. Also reported are low temlating system. Oxygen is circulated through a fritted 10 perature oxidation test results of diluted oil composiglass disc near the bottom of the sample tube at a rate of tions containing only the second additive without the 5 liters per hour. The time required for the absorption boroxarophenanthrene compound. The results of these of 50 millimoles of oxygen per 100 grams of sample is tests are tabulated in Table I; the term BOP refers to taken as the induction period. The longer the inducthe boroxarophenanthrene compound. 7

TABLE I lllo-Diluted Composition Induction Weight per- Period in 302 F. Low Temperature Theoretical cent 1 (Prior Thin Film Test, Hrs. percent of Example Second Additive to thin film Test Tempera- BOP test) ture, F. Remaining Pre-oxidized Control Without Oil BOP None 550 2 1 2 354 0 Tri-(2-hexadeeyl)hydroquinone 2. 74 600 92 79 +100 Tetra-(CCza alkyl)resorcinol 3. 74 550 81 09 +100 Tri-(2-hexadeeyl)catechol 2. 71 600 10 36 28 Tri-(2-hexadecyl)pyrogallol. 2. 78 600 21 39 54 4,4-methylenebis(2,6-di-tertbut 2. 75 550 151 180 84 Tri-(dodecyl)-1-naphthol 2. 25 550 so 100 so N-phenyl-l-naphthylamine 1. 53 550 3 39 8 50 73 1 Weight percentages are equivalent to about 0.035 mole per kg. of composition, except Example 6 (0.065 mole) and Example 3 (0.070 mole). 2 The dilution of the 9-hydroxy-9,lo-boroxarophenanthrene was 0.1% by weight (0.03% in the remaining tests).

3 Test performed at 350 F.

tion period the greater is the oxidative resistance of the oil sample.

OXIDATION TEST RESULTS Example I A white oil was blended with 0.2% by weight of 9-hydroxy-9,10-boroxarophenanthrene. The oil solution was exposed to oxidation at 550 F. for only a single onesecond cycle in the thin-film oxidation test. The resulting oxidized oil was then diluted with an equal amount of white oil (or about a 0.1% theoretical concentration of additive). This diluted blend was tested in the low temperature oxidation test. The induction period was less than one hour. A white oil containing no antioxidant also has an induction period of less than one hour in the low temperature test, indicating that the boroxarophenanthrene had been destroyed. Ultra-violet spectrum analysis confirmed the fact that the thin-film test lasting only one second at 550 F. completely destroyed the boroxarophenanthrene additive.

As a control, an oil blend containing 0.1% by weight of the 9-hydroxy-9,10-boroxarophenanthrene was tested in the low temperature test. The induction period was 354 hours.

Examples 2 t0 8 Using the same white oil, compositions containing 0.3% by weight (0.0153 mole per kg. of composition) of 9-hydroxy-9,10-boroxar0phenanthrene and varying amounts of the secondary additives disclosed in this invention were prepared. Each composition was first exposed to the thin-film oxidation for the full 10 cycles (a total of 10 seconds).

The results obtained from the above described tests indicate that the compositions of this invention have both high and low temperature antioxidant properties. The oil compositions could safely be operated in an engine lubricating system which subjects the oil to hot and coo regions successively.

Table I is indicative of the degree of protection given the boroxarophenanthrene compound at high temperatures. It also shows that the secondary compounds are equally susceptible at low temperatures. The following examples also indicate the protection aiiorded a representative group of these secondary additives by 9- hydroxy-9,10-boroxarophenanthrene.

Examples? to 12 A series of compositions of the white oil used in previous examples, containing 0.035 mole per kg. of composition of a phenol or naphthol alone was subjected to the low temperature oxidation test at 302 F. A second series of compositions, this time containing the phenol or naphthol plus 0.3% by weight (0.0153 mole per kg.) of 9-hydroxy-9,10-boroxarophenanthrene, was also subjected to the same test, except that the test was continued 10 times as long as that of the corresponding composition in the first series.

Following each low temperature test, the compositions were subjected to the thin film oxidation test at the higher temperature. In the following table, the oxidation rate in the thin film test reflects the volume of oxygen absorbed. The lower the oxidation rate the better antioxidation is provided. The 9-hydroxy-9,10-boroxarophenanthrene is again herein referred to as BOP.

TABLE II Hours of Low Temperature Oxidation Example Antioxidants Weight Temperature of Thin Film Rate, ml. Percent Test at 302 F. Test, F. absorbed per mins.

o. 2.25 {Plus BOP 0. so 192 15 1 Completely destroyed.

The data shown in Table II prove that the second additives alone cannot survive for more than several hours at the low temperatures and could then offer no oxidation protection at the high temperature level. However, the combination of the two additives furnishes protection which is greater than either of the two additives separately.

The combined 9-'hydroxy or 9-alkoxy-9,l0-boroxarophenanthrene and polyalkylated naphthol or polyhydroxy phenol or secondary aromatic amine may be used in the presence of other typical oil additives such as detergents, pour point depressors, viscosity control agents, and the like.

Although this invention has been described with the aid of specific embodiments and illustrations, the scope thereof is not limited thereby except as defined in the appended claims.

We claim:

1. A composition capable of withstanding oxidation at high and low temperatures successively comprising a major proportion of a member selected from the group consisting of mineral lubricating oils, synthetic lubricating oils, greases obtained therefrom and hydrocarbon fuels and a minor proportion, sufiicient to provide antioxidant properties thereto, of (1) a boroxarophenanthrene of the formula wherein R is selected from the group consisting of hydrogen, alkyl having from 1 to 25 carbon atoms and R and R" are selected from the group consisting of alkyl, halogen, and haloalkyl, wherein the alkyl radicals have from 1 to 25 carbon atoms, and n is 0 to 4; and (2) an aromatic compound selected from the group consisting formula 3 I B-OR wherein R is selected from the group consisting of hydrogen, alkyl having from 1 to 25 carbon atoms, and

R and R are selected from the group consisting of alkyl, halogen, and haloalkyl, wherein the alkyl radicals have from 1 to 25 carbon atoms, and n is 0 to 4; and (2) an aromatic compound selected from the group consisting of a polyalkylated polyhydroxy hydrocarbyl aromatic compound having up to 7 rings, a polyalkylated monohydroxy naphthol, and an aromatic secondary amine wherein at least one N-substituted group is an aromatic nucleus.

3. The composition of claim 2 wherein the R of the said boroxarophenanthrene is hydrogen.

4. The composition of claim 2, wherein the polyalkylated polyhydroxy hydrocarbyl aromatic compound is a phenol containing at least two hydroxy groups and the alkyl substituents having a total of at least 12 carbon atoms.

5. The composition of claim 2, wherein the polyalkylated monohydroxy naphthol contains at least two alkyl substituents having a total of at least 8 carbon atoms,

6. The composition of claim 2, wherein the secondary amine has the formula Ar-N(H)R wherein AI is an aromatic nucleus of 1 to 2 rings having up to 5 substituents selected from the group consisting of alkyl, halo, and haloalkyl, the alkyl group having 1 to 25 carbon atoms and R' is selected from the group consisting of alkyl, cycloalkyl, haloalkyl, aryl, and alkaryl, wherein the alkyl groups have from 1 to 25 carbon atoms, and wherein Ar and R' may also be members of a cyclic structure of which the amino nitrogen is a member.

7. A lubricant composition capable of withstanding oxidation at high and low temperatures successively com prising a major proportion of a lubricating oil and a minor proportion, sufiicient to provide antioxidant properties thereto, of (1) a boroxarophenanthrene of the formula i am. ung wherein R is selected from the group consisting of hydrogen, alkyl having from 1 to 25 carbon atoms, and

R and R" are selected from the group consisting of alkyl, halogen, and haloalkyl wherein the alkyl radicals have from 1 to 25 carbon atoms, and n is 0 to 4; and (2) a polyalkylated polyhydroxy phenol having at least 2 hydroxy groups and at least 2 alkyl substituents, said alkyl su-bstituents containing a total of at least 12 carbon atoms.

8. An oil composition capable of withstanding oxidation at high and low temperatures successively comprising a major proportion of a lubricating oil and a minor proportion, sufiicient to provide antioxidant properties thereto, of (1) a boroxarophenanthrene of the formula wherein R is selected from the group consisting of hydrogen, alkyl having from 1 to 25 carbon atoms, and

R and R" are selected from the group consisting of alkyl, halogen, and haloalkyl, wherein the alkyl radicals have 10 y from 1 to 25 carbon atoms, and n is 0 to 4; and (2) a polyalkylated monohydroxy naphthol having at least 2 alkyl substituents containing a total of at least 8 carbon atoms.

9. An oil composition capable of withstanding oxidation at high and low temperatures successively comprising a major proportion of a lubricating oil and a minor proportion, sufficient to provide antioxidant properties thereto, of (1) a boroxarophenanthrene of the formula wherein R is selected from the group consisting of hydrogen and alkyl having from 1 to 25 carbon atoms, and

R and R" are selected from the group consisting of alkyl, halogen, and haloalkyl, wherein the alkyl radicals have from 1 to 25 carbon atoms, and n is 0 to 4; and (2) an aromatic secondary amine of the formula wherein Ar and R" are selected from the group consisting of aromatic radicals of 1 to 2 rings and members of a cyclic structure of which the amino nitrogen is also a member.

10. A lubricant composition capable of withstanding oxidation at high and low temperatures successively comprising a major proportion of a lubricating oil and a minor proportion, sufficient to provide antioxidant properties thereto, of (1) 9-hydroxy-9,IO-boroxarophenanthrene and (2) an aromatic compound selected from the group consisting of a polyalkylated polyhydroxy phenol, the alkyl substituents having a total of at least 12 carbon atoms -a polyalkylated monohydroxy naphthol having a total of at least 8 carbon atoms of the alkyl substituents, and an aromatic secondary amine of the formula wherein Ar and R' are aromatic radicals having 1 to 2 rings and Ar and R' may also be members of a cyclic structure of which the amino nitrogen is a member.

11. An oil composition capable of withstanding oxidation at high and low temperatures successively comprising a major proportion of a lubricating oil and a minor proportion, suflicient to provide antioxidant properties thereto, of (1) 9-hydroxy-9,lO-boroxarophenanthrene and (2) a polyalkylated polyhydroxy phenol having 2 to 3 hydroxy groups and 3 to 4 alkyl radicals containing a total of at least 12 carbon atoms.

12. The oil composition of claim 11 wherein the said aromatic compound is tri-(Z-hexadecyl)hydroquinone.

13. The oil composition of claim 11 wherein the said aromatic compound is tri-(2-hexadecyl)catechol.

14. The oil composition of claim 11 wherein the said aromatic compound is tri-(2-hexadecyl)pyrogallol.

15. The oil composition of claim 11 wherein the said aromatic compound is tetra-(C C alkyl) resorcinol.

16. The oil composition of claim 11 wherein the said aromatic compound is 4,4'-methy1enebis(2,6-di-tert.-butylphenol).

17. An oil composition cap-able of withstanding oxidation at high and low temperatures successively comprising (1) 9-hydroxy-9,10-boroxarophenanthrene and (2) a polyalkylated l-naphthol containing from 6 to 30 carbon atoms per alkyl substituent.

18. The composition of claim 17 wherein the naphthol is tri-dodecyl-l-naphthol.

19. An oil compositon capable of withstanding oxidation at high and low temperatures successively comprising a major proportion of a lubricating oil and a minor proportion sufiicient to provide antioxidant properties thereto (1) 9-hydroxy-9,10-boroxarophenanthrene and (2) an aromatic secondary amine wherein the two carbons attached to the nitrogen are members of the group consisting of an aromatic ring and a cyclic structure of which the amino nitrogen is also a member.

20. The composition of claim 19 wherein the amine is N-phenyl-l-naphthyl amine.

References Cited by the Examiner UNITED STATES PATENTS 2,009,480 7/1935 Craig 252-50 X 2,062,676 12/1936 Reitf 252-50 X 2,111,307 3/1938 Bartram 252-50 X 2,121,748 6/1938 Suit 252-50 X 2,191,499 2/1940 Reiff 252-52 X 2,672,448 3/1954 Newman et al 252-52 X 2,691,634 10/1954 Benoit 252-52 3,211,652 10/1965 Hinkamp 252-52 FOREIGN PATENTS 565,012 10/ 1944 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner. 

1. A COMPOSITION CAPABLE OF WITHSATANDING OXIDATION AT HIGH AND LOW TEMPERATURES SUCCESSIVELY COMPRISING A MAJOR PROPORTION OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF MINERAL LUBRICATING OILS, SYTHETIC LUBRICATING OILS, GREASES OBTAINED THEREFROM AND HYDROCARBON FUELS AND A MINOR PROPORTIN, SUFFICIENT TO PROVIDE ANTIOXIDANT PROPERTIES THERETO, OF (1) A BOROXAROPHENANTHRENE OF THE FORMULA 